ARL 12 USS Poseidon

[Fliger747]

40' Motor Launch

Phil:

The boat carried by Poseidon was the same as the one labeled in the Navy Small boat Catalogue on HNSA as 40' Motor Launch. Open and not as fancy as the various "Marked" Personnel boats. Same boat as carried midships on the AO's of the era.

Tom

[Fliger747]

The 40' Motor launch, apparently a MK1 carried aboard Poseidon. I believe this photo was taken securing to a buoy at the Degaussing station on the West Side of Bainbridge Island near Puget Sound Naval Shipyard (PSNS).

Tom

[Fliger747]

Latest trial of the bow boat handling station. Not attached!

[Fliger747]

Not a lot of progress today, up early, played an hour of Ice hockey and later skated for another 1 1/2 hour with a friend. Getting back in shape so little tired. I did design and am printing another variation ( I think I am up to Xi) on the main deck ramp. On Navsource I found a closeup of the surface of the ramp, allegedly wooden covered with canvas and battens. So doing a trial print of that. The technical printing question is how a fairly thin and relatively large surface will print. We shall see. Shouldn't take too long to find out.

I ordered a new IWATA airbrush, which arrived Friday. As it turns out it uses a different air hose size fitting than all my other AB's. So waiting for hose now! It's not patience, it's "Pay-tens".

Tom

[Fliger747]

I tried a printing experiment with I think some success. I had tried printing the main deck forward ramp, as seen on later LST's. The first edition printed using normal support methods came out with a thick and lumpy bottom. One of the drawbacks of SLA printing is it really only does 3 of the four sides. As a doubtful experiment I printed with the ramp resting directly on the platen and to my surprise it came out thin and flat, just right! So when I get the Err-brush hose (tomorrow or Thursday) I'll paint and install.

Cheers: Tom

[Fliger747]

Phil's comment about printing right on the plate, as a mistake, made me think. I have tried to print some thin items but the bottom always comes out lumpy despite good supports. Here I show the bottom of the ramp printed in the normal manner and the support base. I noticed that the base had crisp details of the support boundaries and was quite smooth. Small deduction that perhaps the ramp could be printed flat on the base. The very flat ramp printed on the platen is on the right.

Tom

[BB62vet]

Tom,

The ramp looks good!!! Nothing like R&D to solve problems & answer questions!!

Hank

[Fliger747]

Hank:

Some other tings like flat bottom gun tubs might print better this way. Anything with a large footprint that will adhere well to the platen. The bottom, flat and shiny showing only a mirror of whatever scratches are on the platen.

Tom

[Fliger747]

The hose for the new IWATA "err-brush" arrived at the trusty (still has Chrismas like liens) Post Office. A not dissimilar experience to visiting Russia Post except they have you take a number, a popular option many places there. I am pleased with it's parsimonious use of paint and smooth application. I had just mixed a new batch of deck gray, black, white and pthalo blue in that order. I got a 5 pack of squeeze bottles on E-Bay for a small sum to store my new mixes in. Has a convenient nozzle that rotates up for drop by drop dispensing if desired. After the ramp I painted dries I can do a color/reflectivity comparison. I think it's fairly close.

Tom

[DrPR]

Tom,

I originally tried printing the bitts directly on the printing plate because I thought the large base surface would be adequate.

But I printed them with 0.05 mm steps with six base layers exposed for 40 seconds and the remaining layers for 4.5 seconds (the default for the printer). They all printed with good adhesion to the plate.

But the bottom layers were quite a bit larger than the remainder of the base (see attached photo).

Did you notice any widening of the bottom layers on your print?

Phil

[Fliger747]

Phil:

The ramp is 40 mm wide, so the .25 mm widening of the base was instantly cleared off with a pass of a razor blade. The bitts if printed on a stalk usually need a mild cleanup of the bottom which has a little roundness. A couple of swipes across sandpaper on a smooth surface trims this up.

Tom

[Iceman 29]

It is normal that the 6 layers are wider, this is due to the fact that the 45 second exposure diffuses the UV more widely in the resin.

We notice that the longer the exposure time the more inaccurate the piece is.

For this kind of piece, I don't print on the plate directly, I put supports, then I sand a little the flat surface once the supports are removed.

[Fliger747]

Pascal:

I appreciate that printing with supports is normal, however the degree of sanding to even out the belly for the ramp was rather extreme compared to printing directly on the platen. This was an unusual piece as the width was such that the flaring of the base was so small as to be almost not visible. I tried both and the piece directly on the platen was nearly perfect. I can certainly see that this might not often be the case. In the case of Phil's bitts, triming the edges would be more involved than trimming the small bottom area.

Not a push button part!

Regards: Tom

[DrPR]

Actually, using the recommended (default) print timing the parts I am making come out to almost exact dimensions. I reprinted the bitts on supports - with added pegs to help with location on the model - and the dimensions of the 14" diameter cylinder was 100.2% of the ideal 1:96 dimensions. The measured dimensions were made with a digital caliper, and I would be surprised if it has an accuracy better than 0.2% - maybe not even that good.

The ideal dimension would be 14"/96 = 0.1458". I used three calipers and measured again, and got these measurements: 0.146 (digital), 0.145 (analog), 0.146 (analog). The average is 0.14566666 .... I am quite happy with a -0.0002 inch dimensional error.

I don't buy some of the opinions I have read about exposure times, and no one has offered any empirical data to support their opinions, so I guess I will have to run a series of experiments using a test piece and different exposure times to see what effect it really has on dimensions.

However, the results may be precisely valid only for my printer (specific UV light intensity) and the resin I use (specific sensitivity to UV exposure). But it might yield some general rules for exposure vs. dimensions.

Phil

[Fliger747]

This is an edge on view of the main deck ramps, on the left printed on supports, (bottom side is up). On the right printed on the platen. Note the uneven lumpiness on the part printed on supports.

Phil:

My suggestion is to measure a trial printed item and adjust in whatever slicer you are using, the dimensions. This can be done very accurately to achieve the exact size you wish. Note that at least in Chitubox each vector can be adjusted independently or together for scale. My guess is the real life bitts were manufactured with a little tolerance, especially in wartime.

Tom

[Fliger747]

Many distractions today besides ARL-12. Played ice hockey, skated, researched and found the correct shell holder for the 6.5mm Creedmore. As might be expected all the different providers use different numbering system?

Down to ship shape stuff, attempting to make block and tackle using EZ Line. The stretchiness of the line alleviates one problem but engenders several more. I think I am going to have to make a jig like i did for the APA stuff to hold both blocks in position. Feeding the line through the fairly microscopic holes in the top of the sheaves is accomplished by CA'ing the end of the line to a short length of stretched sprue which feeds through like a needle. Beginning with the boat booms as a trial run for rigging the main boat handling gear.

Ha-rump-ph.

Tom

[Fliger747]

Some minor success with making a block and tackle using EZ line, As with such items with the APA it worked to attach two small close pins to a base and use them to hold blocks in position while they are strung. The very small holes are difficult to string through so a smallish bit of stretched sprue is used as a needle, ca'd to the end of the line. I am also attempting to see how the EZ line works as lifelines. My stanchions are 3D printed and somewhat flexible so can't take tension. Another issue I discovered was painting EZ line isn't great as it remains stretchy and the paint is not. Printing yet another iteration of the triple blocks as getting just the right openings is a challenge in the real world. Eventually I will run out of reasons to procrastinate and tackle the rigging of the cargo booms.

Tom

[Fliger747]

Somewhat further evolution on the stringing of booms and blocks. Currently back to using regular smooth thread. Though the fine sprue CA'd to the thread end works mostly, often the size of the opening in the block is too small to allow this combo to pas smoothly. The latest iteration is to treat the last cm of the thread with CA and cut off at an angle to make a sharp point. This is sharp and still enough to thread fairly well. The main booms have to be threaded when using non stretchable thread. Working ok so far with a few issues. I see why the Kingposts were guyed and did so! Regular thread needs a degree of tension to pull the slack out.

A little more to string which will terminate in the dual cargo winch.

Cheers: Tom

[Fliger747]

Procrastination finally tolls it's bell. I got around to rigging the bow cargo booms and placing the dual winches.

Feeling better so got some work today. I may have or have had the scourge of the Emerald Isle and the little people "O'Micron".

The winch control stands, which I printed quite a few of, are hiding somewhere.

Cheers: Tom

[BB62vet]

Tom,

Glad you're back "in the saddle" as Ronnie Ray-Gun would say!!!

The rigging looks excellent - Was it E-Z line you used? It seems to be the right diameter for the application and everything taut and ship-shape! Great job!!

Hank